We were guessing spark plug issue that caused my 2010 Honda Accord V6 engine excessive vibration before went to the shop. Since we were on a urgent trip back to Los Angeles, we did not have flexibility to choose what shop was reasonable in charging. The charge came out to be $500 dollars for replacing 6 spark pugs, which could be done in an hour. Very surprised and jaw dropping. I should not ignored the tow truck driver who warned me that this Preferred Automotive is vey expensive. Unfortunately I did not take his words....